#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using System;

namespace log4net.Core
{
  /// <summary>
  /// An evaluator that triggers on an Exception type
  /// </summary>
  /// <remarks>
  /// <para>
  /// This evaluator will trigger if the type of the Exception
  /// passed to <see cref="M:IsTriggeringEvent(LoggingEvent)"/>
  /// is equal to a Type in <see cref="ExceptionType"/>.    /// 
  /// </para>
  /// </remarks>
  /// <author>Drew Schaeffer</author>
  public class ExceptionEvaluator : ITriggeringEventEvaluator
  {
    /// <summary>
    /// The type that causes the trigger to fire.
    /// </summary>
    private Type m_type;

    /// <summary>
    /// Causes subclasses of <see cref="ExceptionType"/> to cause the trigger to fire.
    /// </summary>
    private bool m_triggerOnSubclass;

    /// <summary>
    /// Default ctor to allow dynamic creation through a configurator.
    /// </summary>
    public ExceptionEvaluator()
    {
      // empty
    }

    /// <summary>
    /// Constructs an evaluator and initializes to trigger on <paramref name="exType"/>
    /// </summary>
    /// <param name="exType">the type that triggers this evaluator.</param>
    /// <param name="triggerOnSubClass">If true, this evaluator will trigger on subclasses of <see cref="ExceptionType"/>.</param>
    public ExceptionEvaluator(Type exType, bool triggerOnSubClass)
    {
      if (exType == null)
      {
        throw new ArgumentNullException("exType");
      }

      m_type = exType;
      m_triggerOnSubclass = triggerOnSubClass;
    }

    /// <summary>
    /// The type that triggers this evaluator.
    /// </summary>
    public Type ExceptionType
    {
      get { return m_type; }
      set { m_type = value; }
    }

    /// <summary>
    /// If true, this evaluator will trigger on subclasses of <see cref="ExceptionType"/>.
    /// </summary>
    public bool TriggerOnSubclass
    {
      get { return m_triggerOnSubclass; }
      set { m_triggerOnSubclass = value; }
    }

    #region ITriggeringEventEvaluator Members

    /// <summary>
    /// Is this <paramref name="loggingEvent"/> the triggering event?
    /// </summary>
    /// <param name="loggingEvent">The event to check</param>
    /// <returns>This method returns <c>true</c>, if the logging event Exception 
    /// Type is <see cref="ExceptionType"/>. 
    /// Otherwise it returns <c>false</c></returns>
    /// <remarks>
    /// <para>
    /// This evaluator will trigger if the Exception Type of the event
    /// passed to <see cref="M:IsTriggeringEvent(LoggingEvent)"/>
    /// is <see cref="ExceptionType"/>.
    /// </para>
    /// </remarks>
    public bool IsTriggeringEvent(LoggingEvent loggingEvent)
    {
      if (loggingEvent == null)
      {
        throw new ArgumentNullException("loggingEvent");
      }

      if (m_triggerOnSubclass && loggingEvent.ExceptionObject != null)
      {
        // check if loggingEvent.ExceptionObject is of type ExceptionType or subclass of ExceptionType
        Type exceptionObjectType = loggingEvent.ExceptionObject.GetType();
        return exceptionObjectType == m_type || m_type.IsAssignableFrom(exceptionObjectType);
      }
      else if (!m_triggerOnSubclass && loggingEvent.ExceptionObject != null)
      {   // check if loggingEvent.ExceptionObject is of type ExceptionType
        return loggingEvent.ExceptionObject.GetType() == m_type;
      }
      else
      {   // loggingEvent.ExceptionObject is null
        return false;
      }
    }

    #endregion
  }
}
